Indirect bilirubin, also known as unconjugated bilirubin, has a normal reference value of 3.4-17.0 μmol/L. Indirect bilirubin of 25 μmol/L can indicate high bilirubin. Indirect bilirubin is mainly derived from the destruction of red blood cells and is called indirect bilirubin if it has not undergone glucuronidation in the liver. Indirect bilirubin can be changed to direct bilirubin through hepatic metabolism, which is excreted into the bile duct with bile and finally excreted through the stool. If there is a large amount of destruction of red blood cells due to certain reasons, the amount of indirect bilirubin produced will increase, and when the liver cannot completely convert it into direct bilirubin, the level of indirect bilirubin in the blood can be significantly increased. Elevated indirect bilirubin is seen in the following diseases: 1. liver diseases: acute jaundice, acute yellow liver necrosis, chronic active hepatitis cirrhosis, etc.; 2. extra-hepatic diseases: hemolytic jaundice, blood type incompatibility transfusion reaction, cholecystitis, cholelithiasis, etc. A large number of red blood cells in the body are destroyed, and when there is too much indirect bilirubin in the blood, it exceeds the conversion capacity of the liver, causing indirect bilirubin to remain in the blood, thus causing high indirect bilirubin in the blood, often accompanied by yellowing of the skin, yellowing of the sclera, yellowing of the urine and other symptoms, which is also known as jaundice.